Spinal fusion involves joining two or more adjacent vertebrae with an anatomical-fixation implant, and more specifically a spinal-fixation implant, to restrict movement of the vertebrae with respect to one another. For a number of known reasons, spinal-fixation implants are used in spine surgery to align and/or fix a desired relationship between adjacent vertebral bodies. Spinal-fixation implants may include, for example, fixation rods and/or fixation plates having sufficient length to span two or more vertebrae and having sufficient rigidity to maintain a fixed relationship between vertebrae under normal physiological loading of the spine. Each fixation rod and/or fixation plate may be attached to the vertebrae via various bone-fixation devices such screws, bolts, nails, hooks or the like, that pass through the rods and/or plates into the vertebrae, or may be attached to the vertebrae via various bone-fixation devices that are attached to the vertebrae before receiving the fixation rods and/or plates, such as bone anchor assemblies having anchor seats with rod-receiving channels.
Typically, the spinal-fixation implant is provided to the surgeon in a first (e.g., initial or pre-operative) configuration, and must be bent during surgery to a second (e.g., final or post-operative) configuration that is curved so as to align the spinal-fixation implant with the desired, post-operative curvature or contour of the at least one anatomical body. Before bending the spinal-fixation implant, the post-operative spinal contour is determined or approximated using a relatively malleable implant template as a guide or pattern. The implant template has a shape or form such as a rod and/or plate that is similar to the form of the spinal-fixation implant, although the curvature of the implant template initially might not match that of the spinal-fixation implant. The implant template also has a rigidity that is less than that of the spinal-fixation implant. Consequently, unlike the spinal fixation implant, the implant template can be bent by hand. However, due to the ease with which the implant template can be bent, the implant template itself is not suitable for use as a spinal-fixation implant as the implant template would not maintain a fixed relationship between vertebrae under normal physiological loading of the spine.
In operation, the implant template is positioned into the target area of the spine, and the implant template is bent by hand from an initial contour to the desired final or post-operative contour. Upon achieving the final spinal contour, the implant template is removed from the spine, and the spinal-fixation implant is bent using a manual hand-operated bending tool so as to match the post-operative contour of the implant template. As the spinal-fixation element is bent, the surgeon holds the spinal-fixation implant and the implant template adjacent to one another so as to compare the contour of the spinal-fixation implant with the final contour of the implant template. The surgeon continues this process of bending the spinal-fixation implant and comparing it with the implant template until the final contour is achieved. The bending can be performed in multiple steps so as to obtain one or more intermediate contours between the initial contour and the final contour. Once the final contour is achieved, the spinal-fixation implant is implanted into the spine by attaching the spinal-fixation implant to the vertebrae.